Heater winder



B. W. KINYON HEATER WINDER May 13, 1941.

Filed March 30, 1940 lllllllllll I IIIIIIII|]]] INVENTOR. 59/65 :4 K/N YON ATTORNEY.

Patented May 13, 1941 HEATER WINDER.

Brice W. Kinyon, Bloomfield, N. J., assignor to Radio Corporation of *America, a corporation of Delaware Application March 30, 1940, Serial No. 326,844 4 Claims. (01. 140-71) My invention relates to wire winding machines, particularly to machines for winding and folding strands of insulation coated heater wires for cathodes.

The heating element for an indirectly heated center. As the tube is be nt,-itifirst cracks some place along the outside of the bend" where the ceramic is under tension. The wire is then put under tension, and it must eitherbreak' or the ceramic must crumble. If the ceramic crumbles it may shatter a considerable distance either side of the first crack and expose a long section of the wire. It is diflicult to control the amount of insulation that may crumble away, and short circuits between the bare wire of adjacent folds are hard to prevent.

The object of my invention is to fold insulated wire and prevent breakage of the wire and short circuits between the wire at the bends.

Another object of my invention is an improved machine for winding and folding wire covered 3 with brittle insulating material.

The characteristic features of my invention are defined in the appended claims and one embodiment of my improved machine is shown in the accompanying drawing in which Figures 1 and 2 are side and front elevations, respectively, of my novel wire winding mandrel for insulation coated wire, Figure 3 is an enlarged detailed view of. insulated wire wound on my improved machine, and Figure 4 shows a cathode with a heater wound and folded according to my invention.

My wire winding or folding machine comprises a mandrel l rotatable in a journal 2 coaxial with the center line of the mandrel. The windin barrel of the mandrel is preferably lenticular in cross section and may comprise two jaws 3 and 4 hinged at 5 on the rotatable frame 6 so that the jaws may be collapsed to facilitate removal of wire wound on the mandrel. The jaws are biased outwardly by spring 1 against stops on the frame to hold the jaws in fixed spaced relation during winding. It is the purpose of the mandrel to make sharp bends in the wire as the wire is wound on the mandrel with uniform lengths of wire between the bends 50 that when a reel of the desired num.-

ber of folds is removed from the mandrel the folds may be pressed together into a compact bundle and inserted in a cathode sleeve.

The heater wire 8 must be embeddedin a rather thick coating or tube of insulating material 9. The insulating material of necessity must be refractory to withstand the high operating temperatures of the heater and is usually made of fused aluminum oxide or magnesium oxide particles sintered into a hard brittle mass on the wire. If the wire is bent on a fairly large radius of curvaturethe tube may crack any place along the bend .and'hence cause difficulty in locating the precise position-of the bightin the folds. As the legs'of the wire, on either side of the place where the tube first opens, are pressed together the pie-shaped opening in the break. widens andstretches the wire;- If the coating does not crumble away the wire-is placed under such tension as to break the 'wire. Often large pieces of the 'coating are broken off, exposing a considerable length of the heater wire. A long length of exposed heater wire at the bight permits the two legs of the fold to spread and to interleave with other folds and hence short circuit the folds.

I propose according to my invention to bend the coated wire over a sharp edged ridge on the surface of the mandrel. The tension of the wire as it is reeled on to the mandrel is adjusted so that substantially no stress is placed on the coating except at the point where the coating comes in contact with the sharp edged ridges. In the particular machine shown the sharp edged ridges l0 and l l are placed at theends of the lenticular shaped mandrel so that the wire, as it passes over the mandrel, rides over the sharp cutting edge of the ridge. A knife blade may be set into the mandrel with its straight edge extending slightly beyond the winding surface of the mandrel. The blades should be sharp enough to nick or notch the insulation, yet must not be so sharp as to cut the wire pulled onto the mandrel at the reeling tension. A razor blade suitable for shaving may be used, but to prevent cutting of the wire, the blade should be dulled slightly. The extent of dullness or width of the face of the blade should not exceed approximately the diameter of the wire.

One typical insulated heater wire is a tungsten or molybdenum wire about 1.5 mils in diameter embedded in the center of a rather solid aluminum oxide tube 10 to 12 mils in diameter. It appears the knife or cutting edge nicks the ceramic tube and accurately determines the place where the ceramic will first break when the side of the ceramic cylinder first comes in contact with the sharp edge. As the thick walled ceramic tube is bent over the edge the ceramic crumbles away against the side of the blade leaving the end of the ceramic tube substantially flat and normal to the axis of the tube. Sufi'icient of the ceramic is removed and wire exposed to permit the two legs of the fold to be pressed together without stretching the wire. The exposed wire on the other hand is short enough to pull the legs snugly together as they are folded and to hold them to-- gether and prevent interleaving of the legs of the Y The exposed wire of each several adjacent folds. fold, as shown in Figure 4, is a short rigid loop that will not move into contact or short circuit other folds in the sleeve. The clean square break in the insulation distinguishes the bight from the non-uniform ragged break in the insulation of wire wound on the conventional square cornered drum. It is my belief that the sharp edge of the bending ridge slightly nicks the refractory coating and localizes the break, much in the manner a glass rod may be broken at a given point, by notching the rod with a file.

According to another feature of my novel winding machine, a clamp is provided for holding the is crushed and the wire efiectively cleaned for.

welding or brazing purposes. The wire may be cut with a shearing tool 15 guided along the side of the jaw I3. The movement of the wire holding jaws, the shear, and the jaws of the mandrel may for automatic winding be actuated by levers driven in synchronism with the mandrel.

For simplicity of illustration, however, manual When able on its own axis, aplurality of sharp-edged ridges above the winding surface of the cylinder extending lengthwise of the cylinder, said ridge having a cutting edge of a width less than approximately the diameter of the wire to be wound, and said ridges being spaced predetermined distances apart to accurately place spaced bends in wire woundon the mandrel.

2. A winder for wire comprising a mandrel,

' said mandrel being lenticular in cross section in on the surface of the mandrel for bending the wire at spaced points and for accurately predetermining the extent of breakage and shatter of said coating at said points comprising a knifeedged ridge on the winding surface of the mandrel.

4. A machine for bending wire covered with a brittle coating, comprising a mandrel, a ridge along the side of said mandrel, said ridge being sharp enough to notch said coating and localize the shatter of the coating as the wire is drawn over the ridge.

' BRICE W. KINYON. 

